Recently, wireless communication techniques have been implemented by various methods, such as Wireless Local Area Network (W-LAN) represented by Wi-Fi technique, Bluetooth, and near field communication (NFC), in addition to commercial mobile communication network connection. Mobile communication services were initiated from a first generation mobile communication service centered on voice communication, and have gradually been developed to a super-high speed and large capacity service (e.g., a high quality video streaming service). It is expected that a next generation mobile communication service, which is to be commercially available in the future, will be provided through an ultra-high frequency band of dozens of GHz or more (hereinafter, the communication may be referred to as “mm-wave communication”).
The wavelength of a resonance frequency of an antenna device to be used for the mm-wave communication is in a mere range of 1 mm to 10 mm, and the size of a radiator may be further reduced. In addition, in the antenna device used for mm-wave communication, a Radio Frequency Integrated Circuit (RFIC) chip mounted with a communication circuit unit and a radiator may be arranged to be close to each other in order to suppress transmission loss occurring between the communication circuit and the radiator. Such an antenna device may be implemented in a modular form by arranging the RFIC chip and the radiator on a printed circuit board having a width and a length that do not exceed 30 mm, for example, a size of about 10 mm*25 mm.
In general, an operating frequency may be determined depending on the length of the radiator, and as the operating frequency band increases, the size of the antenna device, for example, the size of the radiator that performs a direct radiation operation of wireless signals may decrease. Assuming that a resonance frequency of the antenna device is λ, it means that the radiator may have an electric length of N*(λ/4). Here, N means a natural number. In a case where such an antenna device is mounted in a miniaturized, thinned, and light-weight electronic device, such as a mobile communication terminal, being under mounting space constraints is unavoidable. In particular, the antenna device is mounted within the electronic device in consideration of the radiation performance of the antenna device. Especially, in order to ensure a 360° coverage at the time of mm-wave communication, the antenna device is mounted on an edge portion, such as a corner portion of the circuit board. Since the electronic device have a very thin thickness as compared to the longitudinal size thereof, the antenna device mounted in the electronic device may be easily mounted in the longitudinal direction. That is, the radiator of the antenna device mounted in the electronic device may be easily formed to have a length corresponding to the frequency band in the longitudinal direction. Thus, a radiator having a polarized wave in the longitudinal direction (hereinafter, referred to as a “horizontally polarized wave”) may be easily mounted in an electronic device, may allow easy frequency design, and may have a good radiation efficiency. However, since the electronic device does not provide a sufficient length for allowing the mounting of the radiator of the antenna in the thickness direction of the electronic device, it is not easy to implement a polarized wave in the thickness direction (hereinafter, referred to as a “vertically polarized wave”) as well as to design a required frequency.
In addition, when a plurality of antenna modules are installed along the periphery of a board, a polarization loss occurs due to the interference between adjacent antenna modules. Thus, when the plurality of antenna modules are mounted, it is necessary for the antenna modules to be spaced apart from each other by a predetermined interval which unavoidably causes the integration of the antenna modules to be degraded.